docs: def stop(self):
          """
          Shut the tunnel down.
  
          .. note:: This **had** to be handled with care before ``0.1.0``:
  
              - if a port redirection is opened
              - the destination is not reachable
              - we attempt a connection to that tunnel (``SYN`` is sent and
                acknowledged, then a ``FIN`` packet is sent and never
                acknowledged... weird)
              - we try to shutdown: it will not succeed until ``FIN_WAIT_2`` and
                ``CLOSE_WAIT`` time out.
  
          .. note::
              Handle these scenarios with :attr:`.tunnel_is_up`: if False, server
              ``shutdown()`` will be skipped on that tunnel
          """
          self.logger.info('Closing all open connections...')
          opened_address_text = ', '.join(
              (address_to_str(k.local_address) for k in self._server_list)
          ) or 'None'
          self.logger.debug('Listening tunnels: ' + opened_address_text)
          self._stop_transport()
          self._server_list = []  # reset server list
          self.tunnel_is_up = {}